In U.S. Pat. No. 4,212,272 there is disclosed an idle speed control device for an internal combustion engine wherein the normally available biasing force of the throttle return spring is used at maximum throttle stop extension to initiate threaded re-engagement between a then free-wheelable drive gear and the throttle stop to retract the latter on reversal of the device's actuator motor that powers this gear to position the stop. However, this re-engagement force may not always be available in certain carburetor or fuel injection system control applications or when the throttle stop actuator motor is operated to retract but the throttle return force is held off the throttle stop by the vehicle operator by leaving the throttle pedal depressed.